The 4Cs of diamonds; when they count and when you should ignore them

Each of the 4Cs (Cut, Colour, Clarity and Carat) can play a role in buying a modern cut diamond. The 4Cs are standards set by industry to consistently value diamonds and gemstones. 

People often tell us they have felt overwhelmed when a seller is talking very technically about the 4C’s. It’s important to keep in mind that there are scenarios when a diamond will perform without scoring well across the board and there are even instances when you should ignore a C or two.



The technical knowledge

Cut refers to how well a diamond interacts with light rather than its shape. 

The modern cut diamond has seven criteria to measure its light interaction.

  • Brightness - how well the diamond reflects white light internally and externally.
  • Fire – how well the diamond scatters white light into all the colours of the rainbow.
  • Scintillation – the sparkle pattern of light and dark reflections within the diamond. 

The remaining criteria are weight ratio, durability, polish, and symmetry. 

Why Cut is Important

This is an important C that exclusively applies to a modern cut diamond. If you want your diamond to sparkle and bounce light, you want a diamond with a high Cut value. 

Performance without Cut

Cut won’t matter if it doesn’t perform in real life – remember a Cut rating is measured under artificial light and under magnification. It is possible that the diamond performs well under normal light conditions – under the shop’s light, in the sun. 

It's also possible that a diamond can perform more brilliantly than its rating when not viewed under magnification. 

You won't be wearing your diamond under artificial light OR under magnification so it's important that you consider what a diamond looks like to your naked eye as well as its rating. 

Cut is only considered during the valuation of a round, modern cut diamond. A shallower or a deeper cut diamond will throw light differently. Natural coloured diamonds will also throw light differently, making this C less applicable to these stones. 



The technical knowledge

This standard refers to the stone’s absence of colour. The clearer the hue, the higher rating a diamond will score. Gems are given a colour grade D-Z, D being perfectly colourless, each letter thereafter representing increased hue.

Why Colour is Important

If it’s important to you that your diamond is a colourless diamond, this is an important C. Gradings DEF add a premium because they are all colourless, although keep in mind the difference between these three grades are extremely difficult to detect, even to the well trained eye. 

Performance without Colour

The grading of a diamond for colour is determined when the stone is face down. Diamonds are cut to throw light and scintillation (see Cut) which is distracting to Colour grading. We need to value the Colour of a diamond from the bottom of the stone so the Cut doesn’t draw our eye from this rating. 

This is another C where you may want to consider your own preference by naked eye. Be guided by this rating but also understand that a diamond rated K or L or M can look fantastic face up but grade poorly face down so don’t dismiss a lower rated stone without having a good look at it or discussing it with your designer. 

Diamonds coloured from O and P will have stronger, more intense colour and start to show ‘fancy’ colours. This is when the colour rating can be dismissed entirely because it’s often the point where we want colour. This is where you begin to see your naturally coloured diamonds; champagne, pink, cognac. 



The technical knowledge

Arguably the easiest C to understand. This is literally ‘how big is your diamond’? Carat is a mathematical measurement of the size of your gem. Each carat is made up of 100 points, allowing for precise measurement to the hundredth decimal place.  

Why Carat is important

This is literally the age old debate – does size matter? Certainly, size will matter when it comes to valuing your diamond. Premium is set at each 0.25 intervals. 

Performance without Carat

The size of your diamond comes down to what is important to you. If design is more important to you than the size of your diamond or you’re happy to sacrifice size to invest in a staggeringly brilliant diamond (Cut) then Carat may be negotiable in your hunt for your perfect diamond. 



The technical knowledge

There are two words you’ll often hear when discussing a diamond’s clarity, inclusions and blemishes. Inclusions refer to a diamond’s internal, naturally occurring characteristics and blemishes refer to the external appearance of your diamond. A diamond is valued more highly the less inclusions and blemishes it has. 

Why Clarity Counts

Inclusions CAN affect the scintillation of your diamond. In some cases a poor performance in Clarity will appear to negatively impact the appearance of the cut. 

Performance without Clarity

Inclusions are often not visible to the human eye. When considering two diamonds that look quite similar to each other, one may be valued higher than the other because it has fewer inclusions under microscopic scrutiny. 

Blemishes on a diamond will certainly reduce its value. However during the custom design process a skilled designer can talk to you about using the ring’s settings to disguise or draw the eye away from the blemish, eg using a claw to cover an imperfection.

There’s a lot that goes into choosing a diamond or a diamond ring. Imperial Jewellery has in-house specialists who are happy to talk openly and honestly about a stone’s strengths and flaws. Most importantly we have an enormous selection of loose diamonds to choose from so we don’t have to influence your decision one way or another. We are entirely open to your ideas and happy to share our wealth of knowledge with you to help you find your perfect diamond.


Make an appointment to view our beautiful range of fine jewellery and vintage rings. Meet our Principal Designer to discuss Custom Making your dream ring, choosing from an extensive range of diamonds and gemstones. We believe there are more than enough diamonds, gemstones and precious metals already mined for our jewellery needs. We have amassed a staggeringly beautiful collection of recycled diamonds, gemstones, gold and other noble metals, all environmentally friendly and conflict free.